PLSOIL 120
ORGANIC FARMING AND GARDENING

GLOSSARY OF TERMS

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Acre. 43,560 sq. ft. of land.

Acre furrow slice. A mass of soil occupying one acre of area to a depth of plowing commonly given as six inches. An acre furrow slice is about 2,000,000 pounds, varying with the bulk density of the soil.

Active acidity. A term used to describe the soil acidity that is in the soil solution. It is the acidity that is measured by a common soil test and is expressed as pH.

Adsorption. The attraction of ions or compounds to the surfaces of solids.

Aggregate. Many soil particles held in a single mass or cluster to form a soil structural element, such as a sand-sized particle, gravel-sized particle, crumb, clod, block, or prism.

Alkaline (basic). Above pH 7.

Allelopathy. The effect of one plant on another plant in the soil. The effects are introduced by biologically active chemicals from a living plant or from the decomposing residues of a plant.

Amendment (soil amendment). A material used to alter the chemical or physical properties of a soil and to make the soil more productive. Soil amendments generally are materials other than fertilizers and include substances such as limestone, gypsum, and peatmoss.

Ammonification. The biological process by which ammonium is released from nitrogen-containing organic matter. Ammonification is nitrogen mineralization.

Anaerobic. Without molecular oxygen or living in the absence of air.

Anion. A negatively charged ion.

Available water. The soil water that can be withdrawn by plant roots or the water that is held in soils (or released to plants) between the field capacity and the wilting percentage.

Banding. Application of fertilizer in a concentrated linear zone in the soil, commonly along side the rows of crops. Contrast with broadcasting, which is wide zone application of fertilizer commonly across the surface of the soil or placed or tilled into the soil in an area or zone between rows of crops.

Bedding. Straw, woodchips, sawdust, paper, or other carbonaceous organic matter added to barn floors to absorb liquids from animal excrement and urine. Bedding increases the carbon:nitrogen ratio of farm manures.

Beneficial element. An element that may enhance yields, improve plant growth, or be required by a few plants, but not all plants. Cobalt, silicon, aluminum, sodium, selenium, and other elements.

Biomass. The amount of living material in an organism.

Buffer pH. A measurement of soil acidity, using a specific extract that is resistant or buffered to changes in pH. The value is applied in the calculation of soil lime requirement.

Bulk density. Mass of soil per unit volume of soil. The mass per unit volume of solid particles in the soil is called particle density.

Calibration. When used in conjunction with soil tests refers to research that is performed to interpret soil tests and to correlate crop growth and yields to recommendations based on soil tests.

Carbonaceous matter. Organic matter with a high proportion of carbon and low proportions of other plant nutrients. Generally having a carbon:nitrogen ratio greater than 35:1.

Carbon:nitrogen ratio. The weight ratio of carbon to nitrogen in organic matter. Used as a term to project whether nitrogen will be mineralized from the organic matter and made available for plants to absorb or immobilized from the soil and made unavailable to plants.

Cash crop. A crop grown on land for income or for consumption by humans.

Catch crop. A crop that is grown to lessen leaching of nutrients during a period of time when a cash crop is not on the land.

Cation. A positively charged ion.

Chelate. In plant nutrition, a complex between an organic compound and a metallic plant nutrient, usually a micronutrient.

Chemical fertilizer. A common nondefinitive term used to identify manufactured fertilizers or some concentrated, soluble fertilizers of natural origin. Used in contrast to organic fertilizer.

Chlorosis. The loss of chlorophyll from plant leaves.

Clay. Soil separates less than 0.002 mm in effective diameter. Several types of clay minerals are in soils. Micaceous clays have expanding lattices, which swell and shrink when wetted and dried. Kaolinitic clays do not expand when wetted or shrink when dried. Clay is also a textural class of soil.

Colloid. Organic and inorganic particles of very small size, clay-sized particles, with large surface areas per unit of mass.

Compost. Organic matter that is rotted before it is added to soil. Composting is employed to reduce the carbon:nitrogen ratio, kill plant diseases and weed seeds, and make the organic matter fit to apply to soil.

Complete fertilizer. A fertilizer that supplies nitrogen, phosphorus, and potassium.

Contour. An imaginary line on the land or a line on a map connecting points of equal elevation on the surface of the land.

Cover crop. A crop that is grown to stabilize soil against erosion during a period of time when a cash crop is not on the land. Sometimes used as a term for a green manure crop.

Crop rotation. A planned sequence of crop production in a regularly occurring succession on land. Contrast with monoculture of a continuous crop or with random sequence of cropping.

Denitrification. The biological reduction of principally nitrate (or nitrite) to molecular nitrogen or gaseous nitrogen oxides. Denitrification is a major mechanism for losses of nitrogen from soils that undergo cycles of wetting and drying.

E horizon. A soil horizon between the A horizon and B horizon. Maximum eluviation has occurred in the E horizon, removing organic matter, iron oxides, clay, and other materials and causing the E horizon to be lighter colored than the A or B horizons. Formerly, the A2 horizon.

Early soil. A well-drained soil that warms quickly in the spring for early planting of crops.

Eluviation. The downward movement of solid material from a soil horizon (an A or E horizon). The deposition in the B horizon is called illuvation. Movement may be by leaching.

Essential element. A plant nutrient. One of 17 elements required for plants to complete their life cycles. Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, zinc, copper, manganese, molybdenum, nickel, boron, chlorine. No other element fully substitutes for an essential element, and all plants require the essential element. Having a beneficial effect on plant growth or development is not a characteristic of essentiality.

Exchange capacity. The total ions that a soil can hold or adsorb by electrostatic attraction. Also called cation exchange capacity to identify adsorption of cations by soil particles.

Farm manure. The feces saved from farm animals and applied to land to provide plant nutrients.

Fertilizer. Material that is added to soil to supply plant nutrients. Fertilizers may be identified as being organic, chemical, or complete and having a certain analysis or grade.

Fertilizer grade. The guaranteed minimum percentages of available nitrogen (N), phosphoric acid (P2O5), and potash (K2O) in a commercial fertilizer. Also known as fertilizer analysis.

Field capacity. The percentage of water held in the soil after drainage has ceased essentially. It is the water held in the soil against the downward pull of gravity. Field capacity can be expressed on a volumetric or gravimetric basis.

Fine earth. The soil separates or sand, silt, and clay of soil.

Friable. A physical property describing a loose, crumbly soil.

Furrow slice. The layer of soil that is moved by tillage, usually by plowing. A furrow slice commonly is 6 inches deep. An acre furrow slice is the weight of the soil turned by tillage and is set at 2 million pounds. The weight of acre furrow slice is used in calculations of fertilizer applications, liming, and other soil amendments.

Green manure. A growing, immature crop that is incorporated into the soil to improve soil fertility.

Ground. The soil of the land.

Heavy metals. Metallic elements, some of which are plant nutrients, but commonly used to identify elements considered to be pollutants. These metals may have high densities, exceeding 5 g per cubic centimeter, and may include Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, and Zn and perhaps others, not considered to be metals, such as As.

Heavy soil. A soil that is difficult to till. A condition which refers to soil in which the particles are packed closely together. Clay soils are likely to be heavy soils. The opposite of heavy soil is light soil, which refers to soil composed of relatively large particles loosely packed together. Sandy soils are called light soils.

Horizon. see soil horizon.

Horizon. see soil horizon.

Humus. Dark-colored (black or brown), somewhat stable from of soil organic matter remaining after relatively easily decomposable plant and animal residues have degraded.

Illuvation. The deposition, normally in a B horizon, of materials moved downward by eluviation.

Immobilization. The process by which available plant nutrients in soil are rendered unavailable by microbial consumption. Immobilization usually following incorporation of carbonaceous materials into soils.

Infiltration. The downward movement of water into soil (percolation).

Land. In agriculture, the natural environmental, non-water, area of the Earth in which crops are grown.

Leaching. In soils, the downward movement of materials that dissolve in water as the water passes through the soil. See eluviation and illuviation.

Legume. A plant of the family Fabaceae (Leguminosae), usually associated with nitrogen fixation.

Light soil. The opposite of heavy soil referring to soils that are easy to till. These soils are composed of relatively large particles loosely packed together. The term is applied to sandy soil.

Lime. A material composed of carbonates, oxides, or hydroxides of calcium, magnesium, or both and used to neutralize soil acidity. Commonly, agricultural limestone or mixtures of calciuim and magnesium carbonates.

Lime requirement. The amount of lime that is required to raise the pH of an area of land or mass of soil to a desired value, usually between pH 6 and 7. The limestone required is that to correct the active acidity and reserve acidity.

Luxury consumption. The absorption by plants of more nutrients than the plant needs, but without the expression of any symptoms of toxicity from the nutrients.

Macronutrient. A plant nutrient that is present in plant biomass in relatively high concentrations. Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. The latter six are called soil-derived macronutrients.

Mechanical analysis. A process by which soil separates, sand, silt, and clay, are measured quantitatively by weight.

Micronutrient. A plant nutrient that constitutes a low proportion of plant biomass. Also known as trace element or minor element. Iron, zinc, copper, manganese, molybdenum, nickel, boron, and chlorine.

Mineralization. The process by which plant nutrients in soil organic matter are released by microbial action into soluble or available forms, which plants can absorb. Nitrogen mineralization is ammonification.

Mineral soil. A soil dominated by inorganic matter, primarily sand, silt, and clay, and usaully containing less than 20 % organic matter.

Mulch. A layer of material applied across the surface of the ground.

Necrosis. Death associated with leaves and other plant organs.

Nitrification. The oxidation of ammonium to nitrate in soils or other media. Process is microbiologically mediated.

Nitrogen fixation. A biological process by which gaseous nitrogen in the atmosphere is converted into ammonium. In agronomic practice, the process is symbiotic between legumes and bacteria, which colonize roots of the legumes.

Nitrogenous material. Organic matter that is relatively high in nitrogen in relation to carbon.

Nonexchangeable cations. Positively charged ions that are held in the lattices of micaceous clays. Also referred to as fixed ions, such as fixed potassium.

Nonlegume. A crop that is not a legume. Usually used as a term to identify plants that do not perform nitrogen fixation.

Organic fertilizer. A fertilizer of natural mineral or biological origin, usually processed only physically not involving chemical manufacturing or alteration. Definitions may be provided by a certifying organization. Term used in contrast to chemical fertilizer. Other criteria may include considerations of nutrient concentration and solubility in the naturally occurring material.

Organic soil. A soil that has a high percentage of organic matter, commonly set at >20 %, throughout the A and B horizons.

Pan. A layer of soil that is compacted, hardened, or high in clay. Hardpan, claypan, fragipan.

Particle density.The mass per unit volume of soil particles.

Ped. A natural structural unit in soil.

Percolation. Downward movement of water through the soil. Infiltration.

Permeability. The ease with which fluids (gases or liquids) or plant roots pass through or penetrate into a soil.

pH. An expression of hydrogen ion concentration in soil or a solution. The negative logarithm of hydrogen ion concentration.

Plant nutrient. See essential element.

Phosphorus fixation. A chemical process by which phosphate in solution is precipitated from solution and into relatively insoluble iron and aluminum compounds in acid soils and into sparing soluble calcium an magnesium compounds in basic soils.

Pore volume (pore space).The volumetric percentage of soil bulk that is occupied by air and water not by solid particles.

Potassium fixation. A physical process by which potassium ions are trapped in the lattice of micaceous clays.

Primary mineral. A mineral that has not been altered chemically. Contrasted with secondary mineral (clays).

Puddled soil. Dense, massive, structureless (no aggregates) soil artificially compacted when wet. Characteristic of structureless compressed clay.

Reserve acidity. Soil acidity that is held to the soil particles. Reserve acidity is the major fraction of acidity in soils.

Salinity. The amount of soluble salts in a soil or dissolved in a soil solution or nutrient solution.

Sand. A soil separate with effective diameters from 0.05 to 2 mm. Sand is also a soil textural class in which sand is the dominate separate.

Secondary mineral. A mineral, such as clay, formed from decomposition of primary minerals and reconstition into a new mineral.

Seedbed. Soil or land prepared to promote germination of seed or receipt of transplanted seedlings and to support their subsequent growth.

Silt. A soil separate with effective diameters from 0.002 to 0.05 mm. Silt is also a soil textural class in which silt is a principal separate.

Soil. The collection of surface matter of land that supports plants and that has properties affected by parent material, climate, vegetation, topography, and time and the interactions of these factors.

Soil acidity. The intensity of hydrogen ion concentration in soils. The total acidity is the sum of active acidity and reserve acidity.

Soil air. The gaseous phase of soil; the volume of soil not occupied by solid or water.

Soil amendment. A material added to soils to change their chemical or physical properties.

Soil chemical properties. Characteristics of soil that are defined by chemistry, such as the composition and reaction of soil constituents. Soil pH and nutrient supply are chemical properties contributing to soil fertility.

Soil drainage. The percolation of water through a soil. A well-drained soil is free of saturation and has considerable pore space filled with air.

Soil fertility. An expression of the capacity of soil to support crop production. Fertility is based on soil physical properties, biological, and chemical properties. Often soil fertility is defined as the capacity of soils to provide nutrients to plants.

Soil health. Soil fertility.

Soil horizon. A layer of soil lying about parallel with the soil surface. Characteristics of horizons are used in soil classification or naming. The horizons of a soil are referred to collectively as a soil profile. The most common soil horizons are the A, B, E, and C horizons. These horizons are named according to their position in the profile and degrees of weathering and leaching. Tillage of ground may create a horizon called the plow horizon or Ap.

Soil organic matter. The carbon-containing constituents derived from formerly living organims. Humus is a dark-colored, stable form of soil organic matter.

Soil permeability. See Permeability.

Soil physical properties. Characteristics of soil that are defined by matter and energy. Physical properties include such characteristics as tilth, structure, drainage, water-holding capacity, aeration, and bulk density, which contribute to soil fertility.

Soil profile. A vertical section of soil, showing the horizons.

Soil quality. Soil fertility.

Soil separate. The sand, silt, and clay of soil, particles which will pass through a 2-mm sieve. Also called soil separates. Gravel, cobbles, flagstones, and other constituents larger than 2-mm in diameter are not soil separates but are used as modifiers in names determing soil texture.

Soil solution. The aqueous liquid portion and its solutes in soil.

Soil structure. A soil physical property that is based on the arrangement of soil separates into groups of particles that cohere or adhere by cementation. Aggregates are clusters of many soil particles in a single mass. Ideally aggregates are sand-sized for good soil tilth. Large aggregates are called clods, crumbs, block, prisms, or peds.

Soil surface area. The total surface area of the sand, silt, and clay particles in soil.

Soil testing. An analytical process applied to assess the capacity of soils to supply plant nutrients. Often a rapid, semiquantitative quick test to assess the availability of plant nutrients.

Soil texture. A soil physical property that is determined by the relative proportions by weight of sand, silt, and clay. Organic matter does not affect soil texture but may modify soil structure. Sands dominate in coarse-textured soils, which are referred to often as light soils. Fine-textured soils, called heavy soils, have considerable portions of clays and silt. Loamy soils are medium-textured soils. Soil textural class is part of a name of a soil and refers generally to the A-horizon.

Soil tilth. The physical (structural) properties of soils in relation to crop growth.

Soil water-holding capacity. The water that is held in the fine pores and around the soil particles after water has drained from the large pores. Field capacity is a term for water-holding capacity in a soil, once saturated with water and drained for 2 or 3 days. The wilting percentage is the soil moisture content at which plants in soil permanently wilt.

Tissue testing. An analytical process for assessing the nutritional status of plants by analysis of their tissues. Often a quick test for rapid, on-site assessment and recommendation for needs of fertilization.

Topsoil. Surface layer of soil moved by tillage. Commonly, but not specifically, the A-horizon.

Volatilization. The escape of gaseous materials from a medium to the atmosphere. Ammonia volatilization is a principal mechanism for loss of nitrogen from alkaline soils and composts.

Weathering. The physical and chemical breakdown occurring in rocks and minerals at or near the surface of the earth or in the soil.

Wilting percentage (permanent wilting point). The water content (dry mass basis) of a soil at which plants wilt and do not recover. It is the water that is held by soil and that plants cannot extract.

 Maroon Divider
Description | Syllabus | Notes |Guide | Internet | Lab Manual|Exams and Quizzes|Results|More|
Maroon Divider

Produced and maintained by Your Name Allen V. Barker
University of Massachusetts, Amherst.
last updated - April 25, 1999